Contact structures for vacuum-type circuit interrupters

ABSTRACT

A vacuum-type circuit interrupter is provided having lightweight separable butt arc-initiating contacts, and a pair of stationary generally cylindrical elongated arcing electrodes disposed in spaced relationship, and extending longitudinally of the vacuum circuit interrupter. During opening operation, the lightweight separable arc-initiating contacts are separated to establish arcing therebetween, and the arc is moved, or transferred radially outwardly, to space the relatively small gap between the concentrically arranged stationary cylindrical arcing electrodes, where arc extinction occurs. In certain arrangements, the arcing electrodes are concentric tubes. In other arrangements, the stationary electrodes assume a different configuration, either having a solid generally star-shaped configuration, or a hollow tubular configuration having helical slots, or other configured vent openings therethrough. In the latter case, an external shielding structure may be provided to protect the inner walls of the outer ceramic envelope.

United States Patent [72] Inventors Werner Emmerich Pittsburgh;

Roy E. Voshall, New Alexandria, both of Pa. [21] Appl. No. 808,871 [22] Filed Mar. 20, 1969 [45] Patented Jan. 4, 1972 [73] Assignee Westinghouse Electric Corporation Pittsburgh, Pa.

[54] CONTACT STRUCTURES FOR VACUUM-TYPE CIRCUIT INTERRUPTERS 10 Claims, 9 Drawing Figs.

[52] US. Cl 200/ 144 8, 313/148 R, 200/166 RH [51] Int. Cl 1101b 33/66 [50] Field of Search 200/144 B, 166Bll;313/148,153, 155,233

[56] References Cited UNITED STATES PATENTS 3,328,632 6/1967 .Robinson 313/233 X 3,509,404 4/1970 Rich 3 13/ 148 2,972,032 2/ 1961 Persson 200/144 B 3,014,108 12/1961 Cobine etal..... ZOO/144B 3,185,798 5/1965 Tit u 2001144 B 3,185,799 5/1965 Greenwood et a1 200/144 B 3,366,762 1/1068 Smith,1r. 200/166 BH X 3,372,258 3/ 1968 Porter 200/144 B Primary Examiner-Robert S. Macon Attorneys-A. T. Stratton, Clement L. McHale and Willard R.

Crout ABSTRACT: A vacuum-type circuit interrupter is provided having lightweight separable butt arc-initiating contacts, and a pair of stationary generally cylindrical elongated arcing electrodes disposed in spaced relationship, and extending longitudinally of the vacuum circuit interrupter. During opening operation, the lightweight separable arc-initiating contacts are separated to establish arcing therebetween, and the are is moved, or transferred radially outwardly, to space the relal 3 l\\\\\ X0 PATENTEDJAN M972 3,632,928

WITNESSES INVENTORS Roy E. Vosholl 0nd Werner S. Emmerich d M'QQLR M ATTORNEY DRIVING VELOCITY M/S) MENU-20m 4m: 3.632.928

SHEET 3 [1F 3 1 1 l IOO/ 200 300 400 500 600 700 800 AIR PRESSURE(TORR) CROSS-REFERENCES TO RELATED APPLICATIONS tinent to the present invention.

BACKGROUND OF THE INVENTION Based on prior experience, it appears that the current interruption rating of a vacuum interrupter varies approximately as the square root of the arcing area. It also appears necessary to allow venting for the arcing products, so as to prevent undue buildup of vapor pressure between the electrodes. In addition, some suitable means, such as magnetic fields, have to be employed to move the arc roots and to keep them from concentrating in one spot. All of these requirements must be combined into a reasonably stable mechanical system. Furthermore, it is desirable to provide a long, slim cylindrical geometry rather than a short stout geometry for certain switchgear applications.

As a consequence, high-current vacuum interrupters usuallyemploy massive, intricately designed contacts. Such contacts have the distinct disadvantages in that a large force is required for attaining the fully open position within one-half cycle of the current. For example, the force required to move a 4 pound contact three-fourths inch in 8 milliseconds is about 240 pounds. This assumes that the acting force is constant over the total three-fourths inch of displacement. In addition, the total force has to overcome atmospheric pressure acting on the bellows plus the impact force required to break the weld point of the contacts. Therefore, it is desirable to keep the weight of any moving part to a minimum.

SUMMARY OF THE INVENTION The present invention is particularly concerned with vacuum-type circuit interrupters in which the arc, that initially burns between the stationary and the movable arc-initiating contacts, is transferred to another set of stationary electrodes.

-2 BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a vertical longitudinal section taken through an improved vacuum-type circuit interrupter embodying the The movable arc-initiating contact can be quite light in weight, and the stationary electrodes, to which the arc is transferred, can be as massive as needed.

It is, accordingly, a general object of the present invention to provide an improved high-capacity vacuum-type circuit interrupter of high-speed characteristics and capable of rapidly interrupting high-amperage currents.

Another object of the present invention is to provide an improved vacuum-type circuit interrupter in which light weight abutting separable arc-initiating contacts are engaged and disengaged, and the arcing is transferred outwardly to a pair of spaced stationary generally cylindrical arcing electrodes, where are extinction occurs.

Still a further object of the present invention is to provide an improved high-speed high-capacity vacuum-type circuit interrupter in which novel means are provided for increasing the arcing area, and, additionally, where desired, improved venting means are provided to rapidly vent the arcing vaporized gases and to prevent a buildup of are back pressure.

According to a preferred embodiment of the present invention, there is provided a generally elongated type of vacuumtypecircuit interrupter in which a pair of separable arcing contacts are provided having disposed thereabout a pair of elongated concentrically arranged stationary spaced electrode cylinders. In certain arrangements, the arcing electrodes may assume the shape of a star having elongated recesses provided therealong, or the outer electrode may have a tubular construction with venting slots, in certain instances assuming the form of helically arranged venting slots. In the latter case, an external shielding arrangement is provided to protect the inner walls of the outer ceramic envelope.

Further objects and advantages will readily become apparent upon reading the following specification taken in conjunction with the drawings.

present invention, and the movable arc-initiating contact being shown at an intermediate point in the opening operation; 1

FIG. 2 is a fragmentary view showing a modification of the movable contact structure of FIG. 1;

FIG. 3 is a modified type of vacuum circuit interrupter illustrating a different separable contact arrangement than that illustrated in FIGS. 1 and 2;

FIG. 4 illustrates another modification of the invention;

FIG. 5 illustrates still another modification of the present invention using difierent configured spaced arcing electrodes with a shielding structure applied thereto;

FIG. 5A is a perspective view of the inner stationary arcing electrode structure of FIG. 5;

FIG. 6 is a vertical sectional view taken through a modified type of vacuum circuit interrupter, illustrating an inner vented stationary arcing electrode structure;

FIG. 6A is a perspective view of the inner vented stationary arcing electrode structure of FIG. 6; and, v

FIG. 7 is a graph of the driving velocity exerted on the are as a function of the air pressure in torrs.

DESCRIPTION or THE PREFERRED smsobmams ment. With particular attention being directed to FIG. 1, the

reference numeral 1 generally designates a vacuum-type circuit interrupter. Generally, the vacuum type circuit interrupter I generally comprises a generally cylindrical outerceramic or glass envelope 2, end plates 3 and 4 and a movable contact stem 6 operated by any suitable operating mechanism, and adaptable to cause abutting engagement between a movable contact 7 with a stationary contact 8. As shown, the stationary contact 8 comprises a stationary contact stem 9 having a generally button-shaped inner stationary arc-initiating contact 8 secured thereto. Attached to the external periphery of the stationary button contact 8 is an axially extending stationary cylindrical inner arcing electrode tube, designated by the reference numeral 11, and spaced radially inwardly from an outer stationary concentrically arranged arcing tube, or electrode 12, the latter being secured by a flange portion 12a to the right-hand end plate 4 of the device.

A flexible metallic bellows I4 has one end secured to the movable contact stem 6, and the other left-hand end of the metallic bellows 14 is stationarily secured to the opening 16 provided through the right-hand end plate 4 of the vacuum circuit interrupter 1.

FIG. 1 shows a general contact configuration arranged in such a way that the magnetic field produced by the current in' the contacts 7, 8, and other current-carrying parts of the vacuum switch 1 keeps the are moving until a "natural" current zero occurs, at which time the arc is extinguished. It has been shown that the velocity of an arc in a magnetic field depends upon the current, magnetic field intensity, and the ambient pressure. This investigation has been conducted by S. Yamamura in the Journal of Applied Physics, Volume 2], pages 193-196 (1950). FIG. 7 shows the results of his. investigation concerning the velocity of an arc versus pressure for two different arc currents and the same'magnetic field.

will become significant so that it will move in the Amperian direction.

With further reference being directed to FIG. I, it will be noted that there is provided a contact shaft 6, which is used to move the movable contact 7. This arc-initiating contact 7 has a contacting surface on each side designated by the reference numerals 7a and 7b. When the switch is in the closed position, surface 7a is in contact with stationary contact 8 so that current passes through these sections of the contacts. To interrupt the current, contact 7 is moved away from contact 8 and the arc burns in the intercontact region 18. The movable contact 7 is moved until its surface 7b comes into contact with the contact ring 20. Now a large current loop is formed and the magnetic fields produced by the current in the contacts interacts with the current in the arc. This drives the are outwardly so that the arc will burn between the two concentric cylindrical electrodes 11 and 12, and is magnetically driven in the axial direction along the device. The radial distance between the cylindrical electrodes 1 l and 12 must be less than the spacing between contacts 7 and 8 in order that the arc transfers from contacts 7 and 8 to arcing surfaces 11 and 12.

FIG. 2 shows a modification of the device in FIG. 1 except that the contact surfaces 7b and 20 are eliminated, and a current-carrying strap, or flexible connection 22 connects the movable contact stem 6 to the arcing electrode 12.

FIG. 3 is a generally similar configuration to that of FIGS. 1 and 2, except that the arcing contacts 7, 8' are at the opposite end of the switch. This has the advantage that the bellows 14 is inside of the switch; but, it has the disadvantage that a longer contact stem 6 is needed to move the movable contact 7. The idea of arc transfer is similar to that described for FIGS. 1 and 2.

FIG. 4 is another modification of the present invention. With reference to FIG. 4, it will be observed that again there is provided a pair of end plates 23 and 24 spaced by an external ceramic, or glass envelope 25. Extending inwardly on a stationary contact stem 26 is a stationary contact 8" having a rearwardly extending stationary cylindrical arcing electrode surface 11 Engaging in abutting relation with the stationary contact 8" is a movable contact 7" actuated by a movable contact stem 6 operated by any suitable external means, and secured to one end of a metallic bellows 14. The metallic bellows 14 may, if desired, be protected by a generally cupshaped arcing shield 27. The right-hand end of the metallic bellows 14 may, as before, be fixedly secured to the opening 16 provided in the right-hand end plate 24 of the device.

The contacts 7" and 8 may be, if desired, formed of a suitable nonwelding alloy, whereas the other contact surfaces 7"a and 8"a may be, if desired, formed of copper, or other suitably conductive metal. The stationary arcing electrode cylinders 29,30 may be formed of copper or other highly conductive material.

When the switch is in the closed position, current passes through the contact stem 26, through contact 8" to contact 7" and through contact stem 6. To interrupt the current, movable contact 7 is moved toward the right, so that an arc is initiated between contacts 7" and 8" and the magnetic loop drives the arc to the electrode surfaces 29 and 30. When fully open, the gap between arcing surfaces 7" and 8" is greater than that between the electrodes 29 and 30. Therefore, the arc is transferred to the region between the concentric electrodes 29 and 30. Now the current to contact 7" is fed by an external current strap 32 connecting the electrode stem 6 to the end header 24.

FIG. shows an arrangement somewhat similar to that of FIG. 4, but the stationary arcing structures assume a different form. As shown, the inner stationary arcing electrode structure 33 has a generally star shape with longitudinally extending recesses 33a and outer protruding portions 33b, or the stationary arcing electrodes are the slotted structure 34. In the particular form shown in FIG. 6, the arcing structure 34 has generally helically arranged slots 35 to provide a magnetic field for are movement between the stationary spaced arcing surfaces. To protect the inner surfaces of the outer ceramic envelope 36, an auxiliary shield 17 may be provided, as shown in FIG. 6, to prevent metallic vapors from coating the inner walls of the ceramic envelope 36.

From the foregoing arrangement, it will be apparent that there has been provided an improved high-capacity vacuum type circuit interrupter containing two sets of contacts, or electrodes, one of which is mainly for the purpose of making and breaking contact, and the other set is for arcing purposes only. The movable contact of the contact set is light in weight and relatively small. Any arc, which fonns, is quickly transferred to the second set of contacts or electrodes, where it burns until a current zero. Both electrodes of the arcing set are stationary.

In addition, it will be apparent that the vacuum circuit interrupter described is arranged in a generally elongated manner, so that the device is relatively small in diameter. Additionally, the vacuum device, as particularly illustrated in FIG. 6, has slots or holes made in the shape of bars to allow venting of the arcing products.

For certain applications, it will be apparent that the spacing of the arc-initiating contacts, when open, is larger than the spacing between the stationary electrodes so as to facilitate the transfer of the arc. Moreover, with the construction illustrated, it will be apparent that the magnetic fields are generated by the current to aid in the transfer of arcs from the moving set of contacts to the stationary set of arcing electrodes, and likewise in the axial direction along the stationary electrodes.

With the particular structure illustrated in FIGS. 5 and 6, it will be noted that the spiral slots and the bars in the stationary electrodes 33, 34 set up magnetic fields, which force the arcs to rotate in an azimuthal direction.

From the foregoing description, it will be apparent that there has been provided an improved vacuum-type circuit interrupter adaptable for the high-speed interruption of highamperage currents. The device has a relatively small diameter and the arcing surfaces have been generally lengthened in an axial or longitudinal direction. This provides overall dimensions, which are desirable in many switchgear applications.

Although there has been illustrated and described specific structures, it is to be clearly understood that the same were merely for the purpose of illustration, and that changes and modifications may readily be made therein by those skilled in the art without departing from the spirit and scope of the invention.

We claim:

1. An alternating current electric circuit interrupter of the vacuum type comprising, in combination:

a. a pair of separable arc-initiating contacts;

b. an evacuated envelope surrounding said separable arc-initiating contacts;

c. a pair of stationary conductive electrodes at opposite line potential;

d. one electrode telescopically surrounding the other stationary electrode with an annular space provided therebetween; and,

e. means for transferring the arc from the arc-initiating separable contacts to the annular gap providedbetween said pair of stationary conductive telescopically arranged electrodes with the terminals of the are positioned on said stationary electrodes of opposite line potential.

2. The interrupter of claim 1, wherein the stationary conductive electrodes are concentrically disposed stationary tubes having an annular gap therebetween of less spacing distance than the spacing gap distance between the separable arc-initiating contacts when in the open position.

3. The combination of claim 2, wherein one of the separable arc-initiating contacts is stationary and projects within the evacuated envelope having the inner tubular electrode attached thereto and extending rearwardly longitudinally over the stem portion of the stationary contact.

4. The combination of claim 2, wherein the movable arc-initiating contact makes separable engagement with the end of the inner tubular electrode.

5. The combination of claim I, wherein the inner electrode has a generally star shape.

6. The combination of claim I, where one of the electrodes has a cylindrical configuration with venting slots therein.

7. The combination of claim 6, where the venting slots are helically arranged slots, and shielding means is provided externally thereof to protect the inner surfaces of the envelope.

8. The vacuum-type circuit interrupter combination of claim 1, wherein the inner stationary conductive electrode has an end portion in electrical contact with the end conductive plate of the interrupter.

9. An alternating current electric circuit interrupter of the vacuum type comprising, in combination:

a. a pair of separable arc-initiating contacts;

b. an evacuated envelope surrounding said separable arc-initiating contacts;

. a pair of stationary conductive electrodes;

. one electrode partially surrounding the other stationary electrode with an annular space provided therebetween; e. means for transferring the are from the arc-initiating separable contacts to the annular gap provided between said pair of stationary conductive electrodes with the terminals of the arc positioned on said stationary electrodes; the stationary conductive electrodes being concentrically disposed stationary tubes having an annular gap therebetween of less spacing distance than the spacing gap distance between the separable arc-initiating contacts when in the open position;

g. one of the separable arc-initiating contacts being stationary and projecting within the evacuated envelope having the inner tubular electrode attached thereto and extending rearwardly longitudinally over the stem portion of the stationary contact; and,

h. the outer stationary tubular electrode having an inwardly 5 vacuum type comprising, in combination:

a. a pair of separable arc-initiating contacts;

b. an evacuated envelope surrounding said separable arc-initiating contacts;

c. a pair of stationary conductive electrodes;

d. one electrode partially surrounding the other stationary electrode with an annular space provided therebetween; e. means for transferring the arc from the arc-initiating separable contacts to the annular gap provided between said pair of stationary conductive electrodes with the terminals of the are positioned onsaid stationary electrodes;

f. the stationary conductive electrodes being concentrically disposed stationary tubes having an annular gap therebetween of less spacing. distance than the spacing gap distance between the separable arc-initiating contacts when in the open position;

g. one of the separable arc-initiating contacts being stationary and projecting within the evacuated envelope having the inner tubular electrode attached thereto and extending rearwardly longitudinally over the stern portion of the stationary contact; and,

h. a conducting strap electrically interconnecting the movable stem portion of the movable arc-initiating contact to the outer stationary tubular electrode. 

1. An alternating current electric circuit interrupter of the vacuum type comprising, in combination: a. a pair of separable arc-initiating contacts; b. an evacuated envelope surrounding said separable arcinitiating contacts; c. a pair of stationary conductive electrodes at opposite line potential; d. one electrode telescopically surrounding the other stationary electrode with an annular space provided therebetween; and, e. means for transferring the arc from the arc-initiating separable contacts to the annular gap provided between said pair of stationary conductive telescopically arranged electrodes with the terminals of the arc positioned on said stationary electrodes of opposite line potential.
 2. The interrupter of claim 1, wherein the stationary conductive electrodes are concentrically disposed stationary tubes having an annular gap therebetween of less spacing distance than the spacing gap distance between the separable arc-initiating contacts when in the open position.
 3. The combination of claim 2, wherein one of the separable arc-initiating contacts is stationary and projects within the evacuated envelope having the inner tubular electrode attached thereto and extending rearwardly longitudinally over the stem portion of the stationary contact.
 4. The combination of claim 2, wherein the movable arc-initiating contact makes separable engagement with the end of the inner tubular electrode.
 5. The combination of claim 1, wherein the inner electrode has a generally star shape.
 6. The combination of claim 1, where one of the electrodes has a cylindrical configuration with venting slots therein.
 7. The combination of claim 6, where the venting slots are helically arranged slots, and shielding means is provided externally thereof to protect the inner surfaces of the envelope.
 8. The vacuum-type circuit interrupter combination of claim 1, wherein the inner stationary conductive electrode has an end portion in electrical contact with the end conductive plate of the interrupter.
 9. An alternating current electric circuit interrupter of the vacuum type comprising, in combination: a. a pair of separable arc-initiating contacts; b. an evacuated envelope surrounding said separable arc-initiating contacts; c. a pair of stationary conductive electrodes; d. one electrode partially surrounding the other stationary electrode with an annular space provided therebetween; e. means for transferring the arc from the arc-initiating separable contacts to the annular gap provided between said pair of stationary conductive electrodes with the terminals of the arc positioned on said stationary electrodes; f. the stationary conductive electrodes being concentrically disposed stationary tubes having an annular gap therebetween of less spacing distance than the spacing gap distance between the separable arc-initiating contacts when in the open position; g. one of the separable arc-initiating contacts being stationary and projecting within the evacuated envelope having the inner tubular electrode attached thereto and extending rearwardly longitudinally over the stem portion of the stationary contact; and, h. the outer stationary tubular electrode having an inwardly extending contacting flange portion which makes separable engagement with the rear side of the movablE arc initiating contact.
 10. An alternating current electric circuit interrupter of the vacuum type comprising, in combination: a. a pair of separable arc-initiating contacts; b. an evacuated envelope surrounding said separable arc-initiating contacts; c. a pair of stationary conductive electrodes; d. one electrode partially surrounding the other stationary electrode with an annular space provided therebetween; e. means for transferring the arc from the arc-initiating separable contacts to the annular gap provided between said pair of stationary conductive electrodes with the terminals of the arc positioned on said stationary electrodes; f. the stationary conductive electrodes being concentrically disposed stationary tubes having an annular gap therebetween of less spacing distance than the spacing gap distance between the separable arc-initiating contacts when in the open position; g. one of the separable arc-initiating contacts being stationary and projecting within the evacuated envelope having the inner tubular electrode attached thereto and extending rearwardly longitudinally over the stem portion of the stationary contact; and, h. a conducting strap electrically interconnecting the movable stem portion of the movable arc-initiating contact to the outer stationary tubular electrode. 